BAY POINT — About 4,000 people from 1,400 homes continued to wait for clearance to return to their homes Thursday morning, while crews continued to tackle a fire that sparked inside a Chevron natural gas pipeline vault, authorities said.

The fire continued to burn inside the pipeline vault, a Chevron spokesman said during a press conference Thursday around 7 a.m. Chevreon spent the night releasing natural gas from the pipeline and is in the process of injecting nitrogen into the pipeline “which will extinguish the fire” still burning inside the vault.

Although authorities do not believe there is an imminent threat of an explosion, an evacuation order for about 1,400 homes will remain in place until the fire is extinguished. There are concerns the 12-inch pipeline could still be vulnerable while the fire inside the vault is active.

“Until that fire is extinguished, we’re not comfortable that truly there is no chance that there could be catastrophic failure of that larger pipe,” said Terence Carey, assistant chief of the Contra Costa County Fire Protection District.

Carey estimated that the evacuation order could be lifted mid-Thursday morning. The situation also caused the closure of Willow Cove Elementary School in Pittsburg.

Early Thursday morning, the Contra Costa County Fire Protection District reported on Twitter that “venting of the Bay Point gas line is resulting in a loud, shrieking noise that has been described as a jet-engine-like sound emanating from the Chevron Pipeline Facility on Buchanan Road in Antioch. This is a normal part of the risk-mitigation process. Please do not call 911.”

Evacuees gathered at the Calvary Temple Church on Evora Road in Bay Point, as well as at the parking lot of the Pittsburg/Bay Point BART station, on Bailey Road. BART put out an advisory around 3:30 a.m. encouraging drivers to use another station for parking or to be dropped off at the station, because parking was so limited.

Trains ran normally all morning.

On Thursday morning, Los Medanos College in Pittsburg also opened its gym doors for evacuees.

In a statement late Wednesday, Chevron spokesman Braden Reddall said the company learned around 8 p.m. of a fire caused by an electrical power line falling down that “started a fire near our valve junction on the Northern California Gas Line near Pittsburg, Calif.”

Redall said the company “immediately shut down the line and dispatched a field team to investigate. (Chevron) has initiated its emergency response procedures and is working with the California Office of the State Fire Marshal and local firefighters to evacuate the area as a precautionary measure. (Chevron’s) primary concern is to ensure the safety of responders and the surrounding community. As soon as there are further details, they will be made available.”

There were no immediate reports of any related injuries, but Contra Costa County Fire Protection District firefighters were setting up an incident command location on Poinsettia Avenue. Pittsburg police and Contra Costa sheriff’s deputies are helping to carry out evacuations near the pipeline’s location at Poinsettia and Suisun avenues, ConFire spokesman Steve Hill said.

According to a tweet from KTVU Fox Channel 2, train traffic on tracks in the area has been stopped.

Residents in the area bounded by North Broadway to the west and Summer Way to the east, and Suisun Avenue to the north and Willow Pass Road to the south, should evacuate and plan to remain away overnight, officials said.

That area also was described late Wednesday by the sheriff’s office’s community warning system as Bailey Road and Loftus Lane and from the railroad tracks south to Hanlon Way.

“Take only those essential items you have ready and can carry with you. Pets must be in a carrier or on a leash,” a notice posted on the warning system’s cococws.us site said.

“Lock your windows and doors as you leave. Stay off the phone unless you need to report a life-threatening emergency at your location. However, if you are physically unable to leave your home unassisted, call 911 for help.”